One part of this research project is designed to understand the regulation of viral gene expression during herpes simplex virus (HSV) infection. By construction of recombinant viruses containing synthetic modular promoters , it was found that both the TATA and Initiator elements that constitute an HSV late promoter are normal eukaryotic regulatory elements. Current research is designed to identify the factors that interact with different temporal classes of viral promoters. A second part of this research project is designed to evaluate the feasibility of replication-incompetent HSV gene therapy vectors. Studies during FY97 have focused on establishing a neuronal cell culture system that can be used to evaluate HSV gene therapy vectors for cytotoxic effects, and their ability to express foreign genes. The third part of this research project is designed to evaluate various HSV gene products as potential components of subunit vaccines. Several combinations of plasmid vaccines expressing HSV cell surface proteins and nonstructural regulatory proteins are now being evaluated for their protective effect. The development and evaluation of successful vaccines for herpesvirus infections requires an understanding of the regulation of expression of viral genes during infection, as well as identification of the various viral gene products that can contribute to host immunity. In addition, the development of large DNA viruses, including herpes simplex, as gene therapy vectors, requires an understanding of the regulation of foreign gene expression in viral vectors and evaluation of the safety and toxicity of such vectors. All of the aspects of the research program are directly related to current review responsibilities which include subunit vaccines for herpes simplex infection, replication-defective herpes viruses as vaccines, and herpes simplex vectors for gene therapy. The research program supports policy development regarding the safety and toxicity of virus vectors for vaccines and gene therapy, and the potency of various subunit vaccines. In addition, the research program supports the fundamental science necessary for the understanding and evaluation of each of these new technologies.